They're not entirely separate entities. If we contaminate the water supply of say the Missouri river, the cost of cleaning it up has to be paid at some point. It might be deferrable, but it is not something we can ignore forever.

Some people don't care if a few Little Gray Birds, or varmints, or bugs get wiped out because we(humans) are sloppy with nasty stuff. But wildlife is our "Canary in a coalmine". If we're killing LGBs, then somebody's aunt Sally in Grand Forks is probably getting poisoned too. And if any cost is rising faster than oil, its got to be health care.

The difference is at $200 a barrel, its getting more economical to pay for the clean up, where as at $50 a barrel its obviously better to have never made the mess.